Single channel method and apparatus for automatically optimizing insert editing in a signal recorder

ABSTRACT

A single channel circuit and method for the automatic edit optimization of a recording medium which is operable with a recorder such as a video tape recorder or a disc recorder utilizes the difference between signal outputs from an automatic scan tracking playback head and a record, head to provide a difference signal indicative of the rf amplitude fluctuations caused by scene or data pattern variations of the data stored on the recording medium. A correction signal corresponding to the difference signal is stored, and used as a feedback signal to normalize the gain of a variable gain amplifier. The single channel is switched at a predetermined rate between circuitry coupled to the automatic scan tracking playback head and circuitry coupled to the record head in order to obtain rf amplitude samples from both heads to develop the correction signal. Thereby, the correction signal allows a precise edit optimize so that a subsequent edit operation such as an insert edit can be precisely performed.

This is a continuation of application Ser. No. 07/685,262, filed Apr.12, 1991, now abandoned.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to an application Ser. No. 07/684,628, filedApr. 12, 1991 by Ross Michael Thomas and Colin MacLean Jensen, entitledTWO CHANNEL METHOD AND APPARATUS FOR AUTOMATICALLY OPTIMIZING INSERTEDITING IN A SIGNAL RECORDER assigned to the same assignee, and filedconcurrently with this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to editing information stored in a data file and,more particularly, to automatically optimizing the positioning of arecord head while using an information storage medium such as a magnetictape recorder in editing a magnetic tape or a disc recorder in editing adisc store.

2. Description of Related Art

In editing information such as video signals or audio signals or almostany other signal stored in some storage media such as on a magnetictape, a function known as "edit optimization" has typically beenperformed during the editing session.

It is known that edit optimization includes manually adjusting an editrecording machine so as to provide longitudinal tracking and rotatingscanner phase, which match that of the tape, which is to be edited.Tracking, for example, of a helical record head, typically allows forthe subsequent longitudinal adjustment or alignment of the tape to matchthe helical position of the record head. Edit optimization is typicallyperformed prior to the actual editing function and is typically usefulto set up, or to initialize, or to synchronize, or to align the variouselements of an edit recording machine including the storage medium sothat an "optimized" edit does occur. For example, edit optimization isusually required when making "interchange edits," which are edits of astorage medium such as tape, which has been recorded by one recorder,which is different than a second recorder being used for the editsession. That is, in an interchange edit, the storage medium was writtenusing a first machine but is being edited using a second machine.

In a typical edit optimize, longitudinal tracking is varied across thestorage medium such as a magnetic tape in order to obtain a peak radiofrequency (rf) amplitude signal from a record head during a playback.Note that, in an edit optimize, it is typical that a record head servestwo functions, i.e. in one function, the record head is used to writeinformation on the storage medium while, in the second function, therecord head is used to read information from the storage medium. Adirect current (dc) voltage representing the rf amplitude level isgenerally supplied to a control system, which, in turn, varies thetracking across the tape by way of a suitably programmed microprocessorwithin the control system until a value corresponding to the maximum rflevel is detected and stored in the microprocessor. More particularly,it is known that the microprocessor monitors the rf amplitude whilevarying a reference signal supplied to the conventional control trackcircuit of the tape recorder. When the microprocessor detects the peakrf amplitude, the microprocessor stores the reference signal as adigital value corresponding to the control track position. This storedvalue is thereafter used to provide proper tracking.

In recent state-of-the-art digital video tape recorders such as the VPR®300, which is a D2 composite digital format video tape recordermanufactured by Ampex Corporation, the edit optimization procedure maybe facilitated by various features provided in, for example, an "editoptimize menu" which includes the necessary machine control and displayindications to a human operator which allow automatic adjustments of therequired parameters to perform the edit optimization.

A subtle problem with known edit optimization procedures relates to thefact that record heads need to be positioned over the tracks that arealready recorded on the magnetic tape. Therefore, as newly writtentracks are written over old tracks that are already recorded on themagnetic tape, an edge of the previously recorded track will typicallybe trimmed during the edit process when overwriting the previouslyrecorded track. In that manner, the track is made with an improperwidth. However, if an edit optimization process uses the center of thetrack as a reference, it can align the newly recorded material with thepreviously recorded material.

Further, proper tracking during the editing process may not be possibledue to variations in the data content of the signals already recorded onthe storage medium, whether the data content be video or analog orotherwise or whether the data content be digital or analog or otherwise.The variations in the data content cause frequency variationscommensurate with the different data patterns which make up the recordeddata which, in turn, affects the rf amplitude of the signals on thestorage medium. Such an effect is generally known by the term "patternsensitivity." In particular, variations in frequency cause variations inthe rf amplitudes due to the nature of a digital recording, particularlywhen using a code that changes its frequency spectrum as, for example,does a Miller-squared code. Thus a data pattern, which is recorded on astorage medium at different frequencies, will likely be played back atdifferent rf amplitudes. It is worth pointing out that the effect ofpattern sensitivity exists in analog recording as well as in digitalrecording, although to a much lesser extent in analog recording.

As earlier mentioned, data content variations such as typically relatedto changes in the scenery in the television art, cause problems in thepeaking of the tracking due to fluctuations in the rf amplitudereproduced from a recording of the scenery on a magnetic tape in a videotape recorder. That is, these fluctuations are often caused not only bymistracking with the playback head but also by the variations in thedata content of the recording. It follows then that, when performing,for example, an edit optimize, the pattern sensitivity can causemisleading information to be generated and the misleading informationcan affect the peak rf amplitude measurement. Since proper tracking isassumed upon detecting a peak rf amplitude, if the pattern sensitivitycauses misleading information to be generated, then an improperalignment of a track may be signaled during an edit optimize. If aninsert edit is thereafter undertaken with such an improper alignmentfrom the edit optimize, then the insert edit could result in a poorquality and a visually unacceptable edit when the result is later viewedon a television monitor. Thus, pattern sensitivity in a digitalrecording, such as a recording using, for example, Miller-squaredencoding or any code that changes its frequency content, will be playedback with some rf amplitude variations because of the change infrequency. For example, assume a data pattern is recorded on tape at afrequency of 30 megahertz (MHz) and assume the same data pattern isrecorded on tape at a frequency of 10 MHz. Upon playback, the 30 MHzfrequency signal will likely have a lower rf amplitude than will the 10MHz frequency signal due to the usual losses that occur with increasedfrequency.

SUMMARY OF THE INVENTION

These and other problems are solved in accordance with the principles ofthe present invention, which includes a method and apparatus for, amongother things, differentiating, during an automatic edit optimizingprocess, between rf amplitude fluctuations due to mistracking and rfamplitude fluctuations due to variations in frequency caused by datapattern variations. More particularly, the method and apparatus concerna technique for distinguishing the rf amplitude fluctuations caused bypattern sensitivity from the remaining rf amplitude fluctuations thattruly are caused by tracking alone, to thereby allow proper trackingwhen performing a subsequent edit.

To this end, when in an automatic edit optimize mode, an automatic scantracking playback head of a video tape recorder can be used to playbacka recording. Assume that an automatic scan tracking system isfunctioning. It is then known that the playback head is trackingproperly. Therefore, on the one hand, any fluctuations in the rfamplitude output read by the playback head are not due to mistrackingand, accordingly, on the other hand, such fluctuations in the rfamplitude output read by the playback head must be due to datavariations, or to pattern sensitivity. These fluctuations are determinedand correction values corresponding thereto are stored in a suitablyprogrammed microprocessor. Thus, while a user operator of the method orapparatus is performing an edit optimization, the stored informationderived from the rf amplitude fluctuations caused by pattern sensitivityalone, are applied as a predetermined correction feedback signal tonormalize the record head playback output. Thereby, any fluctuationsremaining in the record head playback output are tracking error signalswhich can be used in a conventional fashion to provide proper tracking.This allows the performance subsequently of a precise insert edit.

More particularly, an illustrative embodiment of the principles of ourinvention includes a switch which alternately supplies (a) the rfamplitude signals generated by the automatic scan tracking playback headto a peak level detector and then (b) rf signals from the record head toa peak level detector. Respective outputs from both the playback headand the record head are low pass filtered to spectrally match the recordhead rf signal. The peak level output from the peak detector isconverted to a corresponding digital signal, which in turn is suppliedto a suitably programmed microprocessor for storage in memory. Thecontents in memory are manipulated by the microprocessor which computesa "correction" signal corresponding to the difference between theplayback head signal and the record head rf signal stored by themicroprocessor. The correction signal is supplied by the microprocessorto vary the gain of a variable gain amplifier in the record head channelto eliminate the effects of pattern sensitivity. Therefore, the signalfrom the variable gain amplifier is due to tracking alone, and a preciseamplitude peak is available responsive to which the record head can becorrectly positioned during a subsequent editing process.

BRIEF DESCRIPTION OF THE DRAWING

These and other advantages of the present invention will become apparentfrom the following detailed description when taken in conjunction withthe accompanying drawing in which:

FIG. 1 is a block diagram depicting a single channel embodiment ofcircuitry for effecting the automatic edit optimize process of theinvention;

FIG. 2 is a block diagram depicting a two channel embodiment ofcircuitry for effecting the automatic edit optimize process of theinvention;

FIG. 3 is a block diagram depicting in further detail portions of thecircuitry of FIG. 2;

FIG. 4 illustrates a plurality of video tracks and audio channels, asideally written on a magnetic tape, and is useful in illustrating theprinciples of our invention;

FIG. 5 illustrates a plurality of video tracks and audio channels, aswritten on a magnetic tape like in FIG. 4 except that the video tracksare misaligned, and is useful in illustrating the principles of ourinvention; and

FIG. 6 illustrates a plurality of video tracks and audio channels, aswritten on a magnetic tape like in FIG. 4 except that some of the audiochannels are misaligned, and is useful in illustrating the principles ofour invention.

DETAILED DESCRIPTION

The following description of the principles of our invention are interms of a magnetic tape storage medium. That is by way of illustrationonly, and not by way of limitation. The principles of our inventionapply equally well to a disc store medium or, for that matter, to anystorage medium which stores data in a manner that, after reading andunderstanding the following detailed description of an illustrativeembodiment of the principles of our invention, resembles a relativelystraight or relatively curvilinear trace or track recording of storedinformation. Further, the principles of our invention are not limited tothe kind of information stored on the storage medium or to the timing orsampling rates described. Although the illustrative embodiment isdescribed in terms of video signals and audio signals being the subjectof an edit optimization, that is also only by way of illustration, andnot by way of limitation, for the information could be video signals,audio signals, both, or still another type of signal and further couldbe digital information, or analog information, or both, or still anotherform of information.

To prepare for an editing session, an edit operator, or user, of theedit optimization system and method to be described could mount thestorage medium such as the magnetic tape to be edited onto any of avariety of recorders for that storage medium such as the VPR® 300, whichis a D2 composite digital format video tape recorder manufactured byAmpex Corporation, for a magnetic tape storage medium. Note that the D2composite digital format is a well known video tape format. Note alsothat the tape recorder which is to be used in the edit session may bedifferent than the tape recorder that was used to store the informationon the tape to be edited, or even the temperature and humidity betweenrecording time and edit time may be different, it being noted that thereis an almost limitless number of variables which could have an effect onthe edit optimization process, where the edit optimization processincludes the process of locating the precise location of the informationto be edited in the edit session. Note further that the editoptimization function occurs before, and typically in anticipation of,the actual edit function, for example, before an insert edit function.The edit optimization function can be thought of as involving a processof preparing or initializing the tape recorder in which the tape andheads are aligned and, using the principles of our invention, areautomatically aligned so that an optimal edit function can thereaftertake place.

A human operator could perform an edit optimization function, whichuntil now has involved the manual adjustment of the longitudinaltracking of the edit recorder machine to match that of the tape to beedited. To help visualize some typical kind of adjustments that are partof the edit optimization function, refer now to FIGS. 4, 5 and 6, eachof which illustrates a magnetic tape 400 with four D2 formatted helicalvideo tracks 410-1, 410-2, 410-3 and 410-4 recorded thereon. Further,the well known D2 format also records four channels of digital audioinformation, which are labelled A1, A2, A3 and A4 and which are recordedat the ends of the helical video tracks 410-1, 410-2, 410-3 and 410-4.Each audio channel is actually recorded twice with identical data beingwritten on the tape at alternate ends of adjacent video tracks toimprove the protection of the written information against corrupted datacaused, for example, by dropouts due to longitudinal scratching of thetape or format and interchange errors as well as to improve editperformance. Also, individual editing of the plurality of audio channelsor the plurality of video channels is made easier by the D2 formatincluding "edit gaps" such as gaps 420 or 421 between blocks of datastored on the individual tracks of the magnetic tape 400.

In the case of an insert edit in which only video is inserted, anideally optimized magnetic tape would insert the new video track(s) inperfect alignment with respect to the audio channels such as isillustrated in FIG. 4. The ideal does not always exist so we can planfor a "misoptimized" magnetic tape. As one example of a misoptimizedmagnetic tape, consider a magnetic tape which could have inserted on itnew, but mispositioned, video tracks such as mispositioned video tracks540 shown in FIG. 5. Note that video tracks 540 are imperfectly alignedwith respect to the audio channels also shown in FIG. 5. Note also thatnot only can newly inserted mispositioned video tracks 540 (versusideally aligned tracks 410-3 and 410-4 shown in FIG. 4) be misalignedwith respect to the audio channels A1, A2, A3 and A4 but the newlyinserted mispositioned video tracks 540 may partially overwrite some ofthe audio channels A1, A2, A3 or A4. For example, observe closely atpoint 530 how the ends of mispositioned video tracks 540 are illustratedin FIG. 5 as overwriting some of audio channels A2 and A4.

As another example of a misoptimized magnetic tape, consider a magnetictape which could have inserted on it new, but mispositioned, audiochannels such as mispositioned audio channels 660 shown in FIG. 6. Notethat audio channels 660 are imperfectly aligned with respect to thevideo tracks also shown in FIG. 6. Note also that not only can newlyinserted audio channels 660 (versus the ideally aligned audio channelsA1, A2, A3 and A4 of FIG. 4) be misaligned with respect to the videotracks 410-1, 410-2, 410-3 and 410-4 but the newly inserted audiochannels may partially overwrite some of the video tracks. For example,observe closely at point 650 how the ends of mispositioned audiochannels 660 are illustrated in FIG. 6 as overwriting some of videotrack 410-3.

With the foregoing description as a foundation and now with anunderstanding of some of the problems related to edit optimization, wenow turn to a more specific description of an illustrative embodiment ofthe principles of our invention. During an edit optimization and beforeperforming an insert edit, the center of a previously recorded track onthe tape to be edited is found by identifying amplitude variations of afirst nature, e.g., by varying the location of the record head withrespect to a track on the magnetic tape (also known as "tracking" in theart) and concurrently detecting a peak amplitude signal that is read, orplayed back, through the record head (also known as "peaking" in theart). However, as previously mentioned, playback rf signal amplitudechanges of a second nature are also caused by changes in the frequencyspectrum due to variations in the recorded data patterns. In accordancewith the principles of our invention, amplitude variations of thissecond nature are identified and removed from the peak trackingamplitude computation. To this end, a detection is made of a playback rfoutput being provided from an automatic scan tracking playback head inorder to derive a signal indicative of changes in the playback headoutput due only to data pattern variations. Prior to a playback rfoutput also being provided from a record head, the playback head rfamplitude is spectrally shaped to match it to that of the record head sothat the difference signal is not affected by specific head propertiesand/or variations in characteristics such as head gap lengths. Afterdetection of both rf signals with equal gain (note the gains need not beequal, but the equality condition is assumed here only to helpillustrate the principles of our invention), the amplitude variation dueto data pattern variations alone is computed, and a correction signalcorresponding to the inverse of the variation is fed back to normalizethe gain of the record head amplifier in the record channel. As aresult, the signal that is derived from the record head amplifier is dueto the effects of tracking alone and can be used to provide precisepositioning of the record head prior to the edit.

Referring to a single channel structure illustrated in FIG. 1, anautomatic scan tracking playback head 112 reads a magnetic tape 110,which can be like magnetic tape 400 shown in FIGS. 4, 5 and 6, andsupplies a playback signal, via a cable 114, to a playback amplifier 116having a fixed gain circuit 118. See, for example, U.S. Pat. No.4,151,570 issued Apr. 24, 1979 for more information about automatic scantracking. An output of the amplifier 116 is supplied to a head switch120 via a cable 134. Switching of the head switch 120 is provided bymeans of a head switch control signal which corresponds to the videovertical rate signal and which is provided on a control cable 122.

A record head 124 supplies a playback signal to a variable gainamplifier 128 via a mode switch 126. The mode switch 126 includes arecord mode contact and an edit play mode contact, with the edit playmode contact being coupled to the variable gain amplifier 128. Therecord contact is coupled to the output of a conventional recordamplifier 127 which supplies the record head 124 with a video recordsignal via a cable 129, for example, as when performing an insert editfunction after the edit optimization function has been completed. Anoutput of the variable gain amplifier 128 is supplied to the head switch120 via a cable 136.

An output of the head switch 120 is coupled to a low pass filter 132,and thence to a linear detector circuit, which may be any of variouslinear detectors such as an average value detector, a root mean squared(RMS) detector or a peak level detector 130, such as is illustratedhere. The cutoff frequency of the low pass filter 132 is selected tomake the frequency response of the playback head channel match thefrequency response of the record head channel. Thus, any differencebetween the output signals from the heads is not due to differences inthe head properties or head characteristics. It may be seen that theinput to the peak level detector 130 is either the amplified andfiltered signal from the playback head 112 or the amplified and filteredsignal from the record head 124, depending upon which position the headswitch 120 is switched to via the vertical rate control signal oncontrol cable 122. An output of peak level detector 130 comprises a pairof signals corresponding to the peak rf amplitudes of the playback head112 and of the record head 124, which are coupled via a cable 140 to ananalog-to-digital (A/D) converter 138, and thence to a suitablyprogrammed microprocessor 142 via a cable 144. The microprocessor 142manipulates the two peak rf amplitudes to provide a correction signalcorresponding to the inverse of the difference between the two peak rfamplitudes. The correction signal 146, which is a measure of patternsensitivity, is supplied to the variable gain amplifier 128 via a cable146 and a digital-to-analog (D/A) converter 148 to vary the gain of theamplifier 128 and to thereby remove the effects of the patternsensitivity. Thus it may be seen that the A/D converter 138, themicroprocessor 142 and the D/A converter 148 comprise, in effect, afeedback loop 150 which supplies the correction signal to variable gainamplifier 128 to normalize the gain in the record head channel, therebyremoving the effects of pattern sensitivity. Thus the signal availablefrom the variable gain amplifier 128 is due to tracking variationsalone, and a value indicative of the corresponding control trackposition is stored via the microprocessor to provide precise tracking ofthe record head during the edit optimization function and prior to theactual edit function. Note that longitudinal control track head 170 canread control track position signals from the magnetic tape in accordwith the D2 format and extend those signals through control trackplayback circuits 175 for providing longitudinal position information tomicroprocessor 142.

Refer now to a two channel approach illustrated in FIG. 2.

In the first channel, an automatic scan tracking playback head 212 readsa magnetic tape 210, which can be like magnetic tape 400 shown in FIGS.4, 5 and 6 or magnetic tape 110 shown in FIG. 1, and supplies a playbacksignal through a low pass filter 232 to a variable gain playbackamplifier 216. The cutoff frequency of low pass filter 232 is selectedto make the frequency response of the first, or playback head, channelmatch the frequency response of the second, or record head, channel,which is later described. Thus, any difference between the outputsignals from the heads is not due to differences in the head propertiesor head characteristics. An output of the variable gain amplifier 216 issupplied to a linear detector circuit, which may be any of variouslinear detectors such as an average value detector, a root mean squared(RMS) detector or a peak level detector 230, such as is illustratedhere. An output of peak level detector 230 comprises a signalcorresponding to the peak rf amplitude of the playback head 212, whichis coupled via a cable 240 to an A/D converter 238, and thence overcable 282 through a track sample memory 260 to a suitably programmedmicroprocessor 242 over cable 292.

In the second channel, a record head 224 supplies a playback signal to alow pass filter 252 via a mode switch 226. The mode switch 226 includesa record mode contact and an edit play mode contact, with the edit playmode contact being coupled to the low pass filter 252. The recordcontact is coupled to the output of a conventional record amplifier 227which supplies the record head 224 with a video record signal via acable 229, for example, as when performing an edit function after theedit optimization function is complete. An output from low pass filter252 is coupled to an input of variable gain amplifier 228. An output ofvariable gain amplifier 228 is supplied to another linear detectorcircuit, which may be any of various linear detectors such as an averagevalue detector, a root mean squared (RMS) detector or a peak leveldetector 250, such as is illustrated here. An output of peak leveldetector 250 comprises a signal corresponding to the peak rf amplitudeof the record head 224, which is coupled via a cable 255 to an A/Dconverter 258, and thence over cable 284 through track sample memory 265to a suitably programmed microprocessor 242 over cable 294.

Thus it may be seen that the first channel including peak level detector230, A/D converter 238, and track sample memory 260 provides a first rfamplitude signal to the microprocessor 242 while the second channelincluding peak level detector 250, A/D converter 258, and track samplememory 265 provides a second rf amplitude signal to the microprocessor242. The microprocessor 242 manipulates the two peak rf amplitudes toprovide appropriate correction signals respectively to variable gainamplifiers 216 and 228, thereby, responsive to the two correctionsignals, obtaining a separate, independent and distinct gain control ineach of the two channels. The track sample memories 260 and 265 areresponsive to head switch signals, scanner tach signals, and timingsignals (here illustratively a four MHz timing signal) provided overcable 280 to control logic 270, for storing and multiplexing therespective rf amplitude signals to microprocessor 242. Thus the rfsignals generated in the first channel can be used to adjust the gaincontrol of amplifier 216 of the first channel and can also be used tonormalize the record head rf amplitude signals with the playback head rfamplitude signals by adjusting the gain control of amplifier 228 in thesecond channel. The rf signals generated in the second channel can beused to adjust the tracking of the record head 224, for example, byautomatically positioning tape 210 with respect to helical record head224, all in response to the control signals from microprocessor 242, andto thereby perform an edit optimize that subsequently precisely locatesthe record head with respect to a track of the storage medium during anedit process.

Note that a longitudinal control track head 271 can read control trackposition signals from the magnetic tape in accordance with the D2 formatand extend those signals through control track playback circuits 275 forproviding longitudinal position information to microprocessor 242.

Turning now to FIG. 3, there is exemplified control logic 270 and tracksample memories 260 and 265. The respective sample memories can besubstantially identical for processing the respective first and thesecond rf amplitude signals. Therefore, the following discussion can belimited to one track sample memory, recognizing that the other tracksample memory is substantially identical. However, before the detaileddescription of those elements a brief incite into the samplingphilosophy and theory appears to be in order.

Tape recorders using the D2 format typically include four record headsand four playback heads, which are grouped in pairs for reading andwriting four tracks of magnetic tape. Typically each pair iselectrically situated so that a playback head can read a track beforethe record head writes that same track. Sometimes such an arrangement iscalled "read before write" in the art. Typically there is a delaycircuit in a read-before-write recorder so that the track that is readcan be processed by the recorder in some designed manner before it iswritten, sometimes rewritten with old data and sometimes written withnew data. For our purposes, on the one hand, edit optimization is moreconcerned with the location of the data on the storage medium and lessconcerned about the content of the stored information. On the otherhand, the insert edit function, which typically occurs after the editoptimization, is typically more concerned about the content of theinformation to be written on the storage medium and less concerned aboutthe location on the storage medium at which the information will bewritten. This makes sense when it is recognized that the editoptimization function occurs first and is useful in the process ofidentifying where the insert edit function will later write theinformation.

Also, the edit optimization function can occur more precisely becausethe sampling rate of the storage medium is increased. This makes sensewhen it is recognized that a higher sampling rate can result in moredata points being made available to be processed in determining a moreprecise location on the storage medium. Further, the edit optimizationfunction can occur more precisely because each pair of playback andrecord heads reads the same track. Fortuitously, with the two channelapproach now being discussed not only are four tracks of magnetic tapebeing read but two heads on each track do the reading, all at a fastersampling rate. The data thusly generated can be processed bymicroprocessor 242 to provide more precise correction signals to moreprecisely locate the tracks on the tape and to more precisely positionthe heads over the tracks, which greatly improves the edit optimizationfunction. In response to the increased precision, it is possible to, forexample, (a) more precisely align a track and/or a head during the editoptimize and prior to an insert edit function writing data on thestorage medium; or (b) more precisely measure the geometrical shape ofthe track, for example, to measure exactly how straight a track may beon a magnetic tape, which, for the VPR® 300 D2 composite digital formatvideo tape recorder manufactured by Ampex Corporation, can be part of aprocess known as a helical scan tracking check; or (c) more preciselymeasure the record head or playback head coplanarity among the pluralityof record heads or among the plurality of playback heads, here of fourrecord heads or of four playback heads; or (d) more precisely verify theoperation of the record head, which is typically used only in recordingbut is here used both for recording and for playback.

Regarding the sampling rate, it may be noted that a scanner tach signalmay be provided by scanner circuitry, which is not part of the presentinvention, as a reference sampling signal. As mentioned earlier, eachtrack on the magnetic tape can include a plurality of blocks of videoinformation where each block includes a video track and two audiochannels which are recorded twice with identical data being written onthe tape at alternate ends of adjacent video tracks. Responsive to thereference sampling signal, each block on a track may be sampled eighttimes--one time for each of the two leading audio channels, four timesfor the video track, and one time for each of the two trailing audiochannels. Note that this emphasizes again the large amount of data thatcan be collected to more precisely perform an edit optimize. Here, eachvideo block is sampled eight times by each of that track's playback headand record head, which gives rise to 16 samples per block, which in turngives rise to 64 samples across the width of the four tracks of onescanner. Note further that the video track and the audio channels aresampled separately and accordingly the data samples may be processedindependently by microprocessor 242. In that manner, and referring tothe earlier discussion of FIGS. 4, 5 and 6, mispositioned video tracksand mispositioned audio channels can be processed independently andoptimized independently, as required, for example, using the read beforewrite process, which was discussed earlier. In view of that teaching,note that a track can, if desired, be rewritten in its entirety or somesegments of the track can be rewritten and other segments left intact,etc. Choices can be displayed to the operator on a display panel andselections may be made by the operator--all these increasedpossibilities flowing from the more precise edit optimization that ispossible in accordance with the principles of our invention.

Head switch signals, scanner tach signals, and a four MHz timing signalcan be provided by other recorder circuitry, which is not part of theinvention, over cable 280 to control logic 270 and therein throughcounter 301 to control PROM 302. Responsive to PROM 302 signals overcable 272, the respective first rf amplitude signals from the respectivefour playback heads, as provided over cable 282, are stored in playbackhead sample stores 310, 311, 312 and 313 of track sample memory 260.Thereafter and responsive to enable signals over cable 292 frommicroprocessor 242 to multiplexors 320 and 321, the first respective rfamplitude signals can be provided from the respective sample stores overcable 293 to the microprocessor for edit optimization processing.Similarly, responsive to PROM 302 signals over cable 274, the respectivesecond rf amplitude signals from the respective four record heads, asprovided over cable 284, are stored in record head sample stores 330,331, 332 and 333 of track sample memory 265. Thereafter and responsiveto enable signals over cable 294 from microprocessor 242 to multiplexors340 and 341, the second respective rf amplitude signals can be providedfrom the respective sample stores over cable 293 to the microprocessorfor edit optimization processing.

Microprocessor 242, as mentioned earlier, can be suitably programmed toperform the edit optimization function. Appendix A includes a sourcecode listing in the C++ programming language for performing the samplingof the rf amplitude signals and for removing the pattern sensitivity.Appendix B includes a source code listing in the C++ programminglanguage for reading the processed data from the program represented bythe code in Appendix A and for performing the edit optimization and forproviding the correction signals to variable gain amplifiers 216 and228.

The foregoing description of the principles of our invention is by wayof illustration only and not by way of limitation. For example, althoughseveral illustrative embodiments of edit optimize system and method inaccordance with the principles of our invention have been shown anddescribed, other alternative embodiments are possible and would be clearto one skilled in the art upon an understanding of the principles of myinvention. Certainly the principles of my invention have utility apartfrom edit optimizing video signals. For example, the edit optimizationof any signal, for example, the edit optimization of a plurality ofgraphics image signals or computer data files or analog concert music,could benefit from the application of the principles of our invention.Accordingly, the scope of our invention is to be limited only by theappended claims. ##SPC1##

What is claimed is:
 1. A circuit for providing automatic editoptimization of a recording in a storage medium, the storage mediumoperable with a recorder, the recorder having a helical record head andan automatic scan tracking helical playback head, wherein there arevariations in a stored data pattern on the storage medium which causemistracking, comprising:first means including the record head forgenerating a signal having amplitude fluctuations due to said variationsand also due to mistracking of the record head; second means includingthe automatic scan tracking playback head for generating a signal havingamplitude fluctuations due only to the variations in the stored datapatterns, said first and second means including means responsive to thegenerated signals for distinguishing between the amplitude fluctuationscaused by said variations and the amplitude fluctuations caused by saidmistracking; and means responsive to the means for distinguishing foradjusting subsequently the tracking of the record head in accordancewith the generated signals.
 2. The circuit of claim 1 wherein theautomatic scan tracking playback head supplies a playback head playbacksignal and the record head supplies a record head playback signal,wherein the distinguishing means includes:detector means for providingthe generated signals in the form of a pair of peak rf signalsrepresentative of the amplitudes of the playback head playback signaland the record head playback signal.
 3. The circuit of claim 2wherein:the first and second means include switch means receiving saidpair of peak rf signals, for alternately supplying the rf signals to thedetector means; and the adjusting means includes microprocessor meansfor generating, in response to the pair of peak rf signals, a correctionsignal indicative of the variations in the stored data patterns.
 4. Thecircuit of claim 3 wherein the adjusting means further comprises:meansresponsive to the playback head rf signal and to the record head rfsignal for spectrally matching the two rf signals.
 5. A circuit forproviding automatic edit optimization of a recording in a storagemedium, the storage medium operable with a recorder, the recorder havinga record head and an automatic scan tracking playback head, whereinthere are variations in a stored data pattern on the storage mediumwhich cause mistracking of the record head, comprising:first meansincluding the record head and second means including the automatic scantracking playback head for generating signals indicative of thevariations in the stored data patterns and also for distinguishingbetween rf amplitude fluctuations caused by pattern sensitivity and rfamplitude fluctuations caused by tracking; wherein the recorder isadapted via the automatic scan tracking playback head to supply aplayback head rf signal and via the record head to supply a record headrf signal; wherein the first and the second generating means include;detector means for providing the generated signals in the form of a pairof alternating peak rf signals representative of the respectiveamplitudes of the playback head rf signal and the record head rf signal;adjusting means including microprocessor means for generating, inresponse to the pair of alternating peak rf signals, a correction signalindicative of the variations in the stored data patterns and foradjusting the tracking of the record head in a subsequent recordingprocess; and wherein the first and second means further includes; switchmeans receiving the automatic scan tracking playback head rf signal andthe record head rf signal for alternately supplying the rf signals tothe detector means.
 6. The circuit of claim 5 further comprising:meansfor switchably operating the switch means at a head switching raterelated to a video vertical rate.
 7. The circuit of claim 5 wherein theadjusting means further comprises:amplifier means coupled between therecord head and an input of the detector means and having a variablegain which is varied in response to the correction signal to cancel themistracking due to the data pattern variations.
 8. The circuit of claim7 wherein the adjusting means further comprises:converter means forsupplying the correction signal from the microprocessor means to theamplifier means; and wherein the microprocessor means includes; memorymeans for storing a tracking signal corresponding to the correctionsignal.
 9. A circuit for providing automatic edit optimization of arecording in a recording medium being operable with a recorder, therecorder having a record head playback signal and an automatically scantracked playback head playback signal, wherein pattern sensitivity andattendant record head mistracking are caused by variations in storeddata patterns on the medium, the circuit comprising:switch means foralternately supplying the playback head playback signal and the recordhead playback signal in response to a predetermined rate signal;detector means responsive to the switch means for generating respectivepeak signals indicative of the playback head playback signal and therecord head playback signal; microprocessor means receiving the peaksignals for distinguishing between rf amplitude fluctuations in theplayback head playback signal caused only by pattern sensitivity and rfamplitude fluctuations in the record head playback signal caused by bothpattern sensitivity and by mistracking, and for generating a correctionsignal indicative of the pattern sensitivity; and means responsive tothe correction signal for adjusting the gain imparted to the record headplayback signal to remove the amplitude fluctuations due to patternsensitivity.
 10. The circuit of claim 9 further comprising filter meansfor receiving and for spectrally matching the two playback signals. 11.The circuit of claim 10 wherein the spectrally matching means is a lowpass filter and the adjusting means is a variable gain amplifier. 12.The circuit of claim 9 wherein the detector means is a linear signaldetecting means such as level detector, an average value detector or anRMS detector.
 13. The circuit of claim 9 further comprising:ananalog-to-digital converter responsive to the playback head playbacksignal and the record head playback signal for supplying the peak rfsignals to the microprocessor means; and a digital-to-analog convertercoupled to the microprocessor means for supplying the correction signalto the gain adjusting means.
 14. A method for providing editoptimization of a recording in a recorder having a helical playback headand a helical record head, wherein there are variations in a datapattern of an associated recorded signal which cause mistracking of therecord head, the method comprising the steps of:generating a playbackhead playback signal having amplitude fluctuations due to saidvariations; generating a record head playback signal having amplitudefluctuations due to said variations and due to the mistracking;detecting a pair of signals corresponding respectively to the recordhead playback signal and the playback head playback signal; determininga correction signal in response to the detected pair of signals whichdistinguishes between amplitude fluctuations caused by the variations inthe data pattern and amplitude fluctuations caused by the mistracking;and adjusting the tracking of the record head in response to thecorrection signal until the record head playback signal peaks.
 15. Themethod of claim 14 including:spectrally matching the playback headplayback signal with the record head playback signal.
 16. The method ofclaim 14 wherein the determining step includes:detecting a differencebetween the amplitude fluctuations of the playback head playback signaland the record head playback signal; and generating the correctionsignal in response to the difference.
 17. The method of claim 14 whereinthe step of generating the playback head playback signalcomprises:supplying the playback head playback signal via an automaticscan tracking playback head;and wherein the method further comprises thestep of: responsive to the playback head playback signal, positioningthe playback head to precisely track while it is playing back.
 18. Themethod of claim 14 wherein the recorder includes a control track circuitand wherein the adjusting step comprises the steps of:varying areference signal to the control track circuit until the record headplayback signal peaks; and storing the corresponding correction signalfor use in positioning the record head.
 19. The method of claim 14wherein the adjusting step comprises the step of:normalizing the gain ofthe record head playback signal in response to the correction signal.20. A system for providing automatic edit optimization of a recording ina storage medium being operable with a recorder, the recorder having ahelical record head which experiences customary mistracking, and anautomatic scan tracking helical playback head, there being variations indata patterns that are recorded on the storage medium which causefurther mistracking of the record head, the system comprising:means fordifferentiating between record head signal fluctuations due to combinedmistracking and playback head signal fluctuations due to variations inthe recorded data patterns; means responsive to the differentiatedsignal fluctuations for generating a correction signal indicative ofonly the variations in the data patterns; and means responsive to thecorrection signal for positioning the record head relative to thestorage medium to subsequently perform the optimized edit recording. 21.The system of claim 20 wherein the automatic scan tracking playback headsupplies a playback head playback signal and wherein the record headsupplies a record head playback signal; andwherein the differentiatingmeans includes; means for distinguishing between the playback headplayback signal amplitude fluctuations that are caused by the datapattern variations and the record head playback signal amplitudefluctuations that are caused by the customary and further mistracking;wherein the generating means includes microprocessor means for providingsaid correction signal in response to said distinguishing means; andwherein the positioning means includes; means responsive to themicroprocessor means for properly tracking the record head whensubsequently performing the optimized edit recording.